Wpływ Bacillus subtilis i Trichoderma asperellum na rozwój sadzonek brzóz zainfekowanych patogenem drobnych korzeni Phytophthora plurivora

Phytophthora pathogens cannot be controlled with well−known fungicides, because as oomycetes they do not synthesize chitin and ergosterol. Phytopathogenic microorganisms of Phytophthora genus offers an alternative to pesticides. The aim of the study was to understand the interactions among the host silver birch (Betula pendula), a common forest tree species in Polish lowlands and in lower mountain locations, and its primary pathogen Phytophthora plurivora as well as potential Biological Control Agents Bacillus subtilis and Trichoderma asperellum. The 2−year−old silver birch seedlings were selected for this experiment. Interactions between P. plurivora and B. subtilis, producing peptide antibiotics including polymyxin B and subtiline, stimulated growth of birch seedlings. Comparing to the control a stimulation of both height and root collar diameter of plants was observed when B. subtilis was added into the soil of pots. It is a saprophyte, decomposing organic compounds of plant origin. However, the application of bacterium into the rhizosphere soil stimulated more shoots growth than roots. The application of T. asperellum into the soil stimulated development of roots, and in consequences the above−ground parts of plants. However, in the combination with pathogen, T. asperellum protected the roots only partially. The presence of pathogen and its antagonists increases the biomass of birches compared to control plants. Chlorophyll fluorescence studies proved better parameters like total performance index (PI total) after application of B. subtilis, in contrast, interaction between B. subtilis and P. plurivora negatively affected photosynthesis causing weakening of plants. The higher content of carboxylic acids, observed in the variant with T. asperellum + P. plurivora, indicates the initiation of biochemical defence processes in birch leaves cells.